1. Field of the Invention
This invention pertains to vibration damping handle grips and the process for making them.
2. Description of the Prior Art
The use of vibration damping handles is well known in various applications including, but not limited to, power tools, hand tools, handle bars, and athletic equipment. These applications generally involve the use of a plastic or rubber-like object placed over the handle during the manufacture of the original equipment or as a replacement grip.
Attempts have been made to isolate the vibrations from these sources by providing vibration damping handles and grips involving the use of a tape, a removable sleeve, or an elastomer cured directly to the product's handle. For example, a hand grip has been described, in U.S. Pat. No. 4,476,742, as a grooved and ridged tape helically wound onto a handle of sporting equipment, hand tools and other articles generally gripped by hand during use. The tape may be effective in providing a measure of traction and some cushioning effect against the hand of the user; nevertheless, the reference fails to disclose vibration damping properties which address the potential health and safety problems associated with excess vibration imparted to the operator's arms and hands over long periods of use. In addition to this apparent deficiency, tapes of this type are suspect in demanding applications such as in power tools used in the construction industry where handles are subjected to heavy use and rough treatment.
Another suggestion describes vibration damping in the form of shrink-wrap tubing systems (U.S. Pat. No. 4,168,754). This method includes placing a vibration damping material over the intended working part of an impact tool; placing a heat shrinkable sleeve over the vibration damping material, and fixing it in place by directly applying a heat source to the tool. At the elevated temperatures the heat shrinkable sleeve decreases in diameter providing a means for the enclosed liquid-like vibration damping material to be mounted to the tool.
This suggestion provides a means for damping vibration and associated sound from the tool. Many disadvantages of this type of system however, including difficult application of the liquid-like vibration damping material and the heat shrinkable sleeve, lack of durability during heavy use over long periods, and a high cost per unit relative to other methods, make use of this apparatus and process impractical for many applications.
Other suggestions include some form of sleeve, removable or permanent, as a grip shield, handle grip, or vibration insulator.
In U.S. Pat. No. 4,415,954 there is described a sleeve of slip resistant material which is forced over the end of a lubricated handle. This method provides improved gripping and protection from the abrasive action of a knurled handle of essentially static items, thereby not requiring, or providing, any vibration damping function.
Handle grips have also been described in the art (for example, U.S. Pat. Nos. 4,381,579; 4,416,166; and 4,739,674) which provide more comfort and traction for the user, and a means to prevent injuries. Because such handles may be subjected to heavy use however, there is a need to provide a grip constructed of a harder material that is more durable. The use of harder, more durable materials for handle grips compromises the vibration damping ability of the handle. Generally, the inventions which attempt to address durability and vibration damping are difficult to apply, and expensive.